Is that you could basically respond with "I know you are, but what am I?" and logically there's no refutation of that comeback.

Sauce for the goose is good for the gander.
What is gratuitously affirmed can be gratuitously denied.

And Our Lord Himself addressed this issue!
(St. Matthew chapter 12)
[27] And if I by Beelzebub cast out devils, by whom do your children cast them out? Therefore they shall be your judges.

Apparently there were exorcists in the Old Testament. How do they cast out devils? If they say "with God's power" then Jesus could say "Exactly. That is how I was casting them out."

I know this is incredibly basic, but something clicked or became simpler for me this morning, so I wanted to share my thoughts.

For example, a Pfeifferite said in his newsletter years ago that people follow Bishop Williamson because they like Downton Abbey and swoon for anyone with an Oxford (high class English) accent.
But why does he follow Fr. Pfeiffer? Oh that has NOTHING to do with cult of personality. It's completely about the doctrine, and supporting a priest doing good work.
Hypocritical much? That's what got me thinking about ad-hominems in general, and inspired this thread.

In fact, the psychological phenomenon of projection is often involved as well. Back to my original example: Fr. Pfeiffer could say anything, even contradict himself, and his cult members will go along with it. He could go from virulently anti-sedevacantist, to openly supporting sedevacantism (e.g., seeking consecration from a sedevacantist bishop) and his cult members will go with the flow. Why? because it's 100% a cult of personality -- in this case, a literal cult. But when they accuse their opponents (in the Resistance for example) of "following Fr. _____ like a cult", it actually has no basis in fact. They're talking about themselves. It's classic projection.

Or when antifa calls conservatives "Fascists". Or when the left calls conservatives "naz|s". You're close! Just point that finger back at yourselves and you'll be telling the Gospel truth.